1. Field of the Invention
The present invention relates to underreamers used in the perforation of wells, and more particularly, oil wells.
2. Description of the Related Art
Underreamers are tools used to expand drilled wells, such as oil wells, and many times these wells extend for several thousands of feet below the surface. To achieve this, sections are added as the drilling process progresses. However, when a well collapses, the entire apparatus needs to be taken out and different tools installed to meet the requirements.
The present invention overcomes the shortcomings of other underreamers because it also includes cutting teeth, mounted at the lower end of the underreamer apparatus, that are designed to continue operating even when the drilling well has collapsed. Also, sometimes a section of the well needs to be enlarged, requiring a different tool. Thus, the apparatus does not have to be removed from the drilling well when this happens avoiding having to pull out the tools and consequently representing considerable savings in operating costs. The teeth, being aligned and spaced apart, permit the underreamer to continue removing dirt from the bottom.
Also, the present invention discloses blade assemblies mounted to the lateral of the body that have double functionality, namely, enlarging a well section and cutting a pipe casing previously installed inside the well.
One of the first U.S. patents for underreamers is U.S. Pat. No. 1,478,306 issued to Sweetman in 1920. It provides for the use of lateral cutters which are raised through the application of pressurized water to a spring-loaded piston head. No cutting teeth at the lower end of the underreamer or removable water constricting socket member, however, are disclosed.
Another related reference is U.S. Pat. No. 4,461,361 issued in 1984 to Fuchs. The end cutters 16, however, would be obstructed if the well collapses since they will be trap the mud making it impossible to move.
Another related patent reference corresponds to U.S. Pat. No. 5,139,098 issued to Blake in 1992. This patent discloses a Combined Drill and Underreamer Tool that includes an underreamer tool with a drill bit assembly at the end. The cutting arms of the underreamer tool are actuated (expanded) against their retracted spring biased position. A fluid by pass is provided to clean the drill bit assembly which is routed from a distribution chamber 35, through coaxial lateral ports 42, through bypass conduit 54 along elongated channels 47, and into internal chamber 70. The fluid is them directed towards drill bit 24. With a spool-valve like device 110, up to 30% of the fluid is diverted to the underreamer to actuate it and lubricate it. Thus, the drill fluid is divided in two independent paths. More important, the circuitous path of bypass conduit 54 loses its cleaning pressure by the time it reaches internal chamber 70. Also, having a body of water (to make it worse is variable or bypassable) at the periphery of the tool introduces an additional load to the rotation motor. Finally, having bypass conduit 54 flush with the peripheral wall exposes the device to being punctured and causing leads. The present invention, on the other hand, directs the pressurized drilling fluid towards the cutting teeth, at an angle, and the latter act as a water impeller to create a turbulence that dislodges any debris and pushes it upwardly. Depending on the soil characteristics, constricting sockets of different dimensions can be selected to prevent overflow, while still being sufficient, after a predetermined magnitude of pressure, to overcome the spring bias.
Other patents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention.